Highly efficient and durable Ga-doped Ni/Al2O3 catalyst enhanced by interfacial Ga3+ for low-temperature ammonia decomposition

Ammonia is a promising hydrogen carrier for producing COx-free hydrogen. However, its decomposition suffers from high reaction temperatures. This study reveals that trace Ga doping markedly boosts the low-temperature activity of Ni/Al2O3 catalyst for ammonia decomposition. The Ga-doped Ni/Al2O3 catalyst achieves 92.0% ammonia conversion at 500 oC and weight hourly space velocity (WHSV) = 30,000 mL gcat−1 h−1. Kinetic experiments demonstrate that the introduction of Ga species alleviates catalyst hydrogen poisoning. Further studies confirm that Ga preferentially segregates on the catalyst surface and disperses around Ni nanoparticles. Interfacial Ga species facilitate hydrogen spillover from Ni to the Al2O3 support, which promotes the enrichment of adsorbed N* species and reduces their recombination temperature on the Ni surface. This work develops an efficient and stable Ni-based catalyst for low-temperature ammonia decomposition and provides a strategy for optimizing catalytic performance via the regulation of interfacial hydrogen transfer. Ammonia could enable carbon-free hydrogen production, but efficient decomposition at low temperatures remains difficult. Trace gallium helps nickel catalysts remove surface hydrogen, markedly boosting low temperature activity.